1. Field of the Invention
The present invention relates to a chemically amplified positive resist composition for use in microfabrication of semiconductor.
2. Prior Art
Semiconductor microfabrication employs a lithography process using a resist composition. In lithography, theoretically, the shorter the exposure wavelength becomes, the higher the resolution can be made, as expressed by Rayleigh's diffraction limit formula. The wavelength of an exposure light source for lithography used in the manufacture of semiconductor devices has been shortened year by year as g line having a wavelength of 436 nm, i line having a wavelength of 365 nm, KrF excimer laser having a wavelength of 248 nm and ArF excimer laser having a wavelength of 193 nm. F2 excimer laser having a wavelength of 157 nm seems to be the next-generation exposure light source. Further, as the exposure light source of the subsequent generation, soft X ray (EUV) having a wavelength of 13 nm or shorter has been proposed as the exposure light source following the 157 nm-wavelength F2 excimer laser. In the meantime, as the lithography technology of the next generation, immersion lithography using ArF excimer laser having a wavelength of 193 nm or F2 excimer laser having a wavelength of 157 nm is proposed.
Since light sources having shorter wavelength than that of g line and i line, such as excimer laser and the like have low illumination, it is necessary to enhance the sensitivity of a resist. Consequently, there are used so-called chemically amplified resists utilizing the catalytic action of an acid produced from a sulfonium salt and the like by exposure and containing a resin having a group being dissociated by this acid, as seen, for example, in JP-A-2000-137327.
However, contact hole pattern obtained by such known chemically amplified resist compositions are not satisfactory, though they provide good line and space patterns.